In the field of optical data communication, increasingly complex devices are developed with ever growing numbers of integrated and simultaneously operated optical fibers.
Such devices, like for example, optical switching fabric integrate more than thousand optical fibers and perform simultaneous switching operations between the individual fibers. In order to efficiently handle such a large number of integrated fibers, special constructive efforts are necessary. Sub components like, for example, optical connectors are designed to tightly combine and hold fibers such that their ends are planar arrayed and parallel oriented on an output face. Information carrying light beams propagate towards and away from the fiber ends embedded and coplanar polished together with the output face. The efficiency of the beam propagation in and out of the fiber ends is highly dependent on the surface quality of the output face. Several fabrication steps are performed to insert and bond the fiber ends and then grind and polish the output face.
During the lifetime of an optical switching fabric, the output face needs to be protected against humidity to prevent corrosive damage. An optical connector may be designed to hermetically seal the output face. For that purpose, a glass plate may be placed on top of the output face. In such a case, the gap between the output face and the glass plate is filled with an optical gel that has substantially the same refractive index as the glass plate. In that context it is referred to the concurrently filed patent application for “Apparatus for Holding a Fiber Array” of Janusz Liberkowski and Steven Nasiri. While applying the gel and sealing the gap between the glass plate and the output face it is crucial that entrapped air bubbles are avoided.
Conventional methods where the gel is applied under atmospheric air pressure have proven insufficient. There are three main reasons for that. Firstly, microscopic air bubbles tend to adhere to the output face while the gel is applied. The air bubbles appear to adhere at the boundaries between the four materials present at the output face, which may be silicon of the insert in which the fiber ends are inserted, glass of the fiber, glass plate end and epoxy with which the fiber end is bonded. When the gel is pressed between surface of the silicon and surface of the glass, air bubbles are squeezed out from the gel layer.
Secondly, the unmixed gel components themselves may contain entrapped air. And thirdly, immediately prior gel application, the individual gel components are mixed to initiate the chemical reaction that causes the curing of the gel. During the mixing, air may also be entrapped.
These three reasons to the contrary, the mixed gel needs to be kept under atmospheric pressure to avoid a well-known cooking of the gel in the vacuum where gas bubbles are formed within the gel.
Therefore, there exists a need for a special method and apparatus for applying a gel to a face and to seal a gap between two faces without entrapped air bubbles and to avoid cooking of the gel. The present invention addresses this need.